fix: process request body once at EOS and correct status/filter bugs

[fzipi]

Summary

• Process the request body once at EOS instead of once per bucket, by moving msc_process_request_body() into the handler phase (hook_request_late) and only buffering chunks in the input filter
• Register hook_request_late via ap_hook_handler (not fixups) and read the body with ap_setup_client_block()/ap_get_client_block() so the input filter actually runs; create the transaction context in hook_insert_filter if it doesn't exist yet
• Set r->status in addition to r->status_line so interventions return the configured HTTP status instead of a default
• Fix input_filter() calling ap_remove_output_filter() instead of ap_remove_input_filter()
• Check the apr_bucket_read() return value in output_filter()
• Replay the buffered request body to the real content handler: hook_request_late drains the body via ap_get_client_block() before the real handler runs, which previously left downstream handlers (CGI, mod_proxy_fcgi) with an empty or truncated body. The input filter now keeps a copy and replays it, honoring nbytes so large bodies aren't handed back in one oversized chunk; r->read_length/r->remaining are reset so classic client-block API handlers also see the body
• Return HTTP_BAD_REQUEST when ap_get_client_block() reports a -1 read error, instead of treating it as EOF

Test plan

• Built the connector and confirmed the module loads in Apache
• Verified via Docker smoke test (see companion PR) that normal requests return 200, query-string rule matches return 403, and status codes set by interventions are passed through correctly
• Built against libmodsecurity v3 with real Apache/APR headers; no new compiler warnings
• End-to-end test against Apache 2.4.68 + mod_cgi: a 20,000-byte POST body arrives byte-for-byte identical at the CGI handler; a rule-triggering POST is still blocked with 403 and the body never reaches the handler

Summary by CodeRabbit

• Bug Fixes

Summary by CodeRabbit

• Bug Fixes
  • Improved request-body handling to ensure complete processing before security inspection.
  • Ensured request bodies remain available to application handlers after inspection.
  • Added fallback handling for requests missing an initialized security context.
  • Improved response-body read failure detection and logging.
  • Ensured generated error responses include the correct status code and status line.
  • Improved end-of-request processing and input-filter cleanup.

[fzipi]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 230e14d and db76acb.

📒 Files selected for processing (3)

• src/mod_security3.c
• src/mod_security3.h
• src/msc_filters.c

🚧 Files skipped from review as they are similar to previous changes (3)

• src/msc_filters.c
• src/mod_security3.h
• src/mod_security3.c

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📝 Walkthrough

Walkthrough

Transaction contexts now initialize request-body replay state. Apache reads request bodies during the handler phase, while the input filter buffers and later replays them. Response read failures and generated error status assignment are handled explicitly.

Changes

Request body processing

Layer / File(s)	Summary
Transaction context and filter setup src/mod_security3.h, src/mod_security3.c	msc_t now stores request-body processing state and a replay brigade. Missing contexts are created during filter setup and late request handling. hook_request_late runs in the handler phase.
Body buffering, replay, and late processing src/msc_filters.c, src/mod_security3.c	The input filter buffers request-body chunks through EOS. Replay helpers return the buffered body to the content handler. hook_request_late reads and processes the complete body through Apache client-block handling.
Response filtering and error status src/msc_filters.c, src/msc_utils.c	Response-body read failures are logged and returned. Error buckets now set both the request status code and status line.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant Apache
  participant hook_request_late
  participant input_filter
  participant ContentHandler
  Apache->>hook_request_late: invoke early request handler
  hook_request_late->>Apache: configure and read the request body
  Apache->>input_filter: deliver request-body buckets
  input_filter->>input_filter: buffer chunks through EOS
  hook_request_late->>ContentHandler: process the buffered body
  ContentHandler->>input_filter: request body reads
  input_filter-->>ContentHandler: replay buffered buckets

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 55.56% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 9 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main changes: process the request body once at end of stream and fix related status and filter handling.

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Actionable comments posted: 1

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Inline comments:
In `@src/mod_security3.c`:
- Around line 405-435: Update the request-body handling around
ap_get_client_block in hook_request_late to preserve all consumed body data for
the configured content handler, using a replayable input-filter or equivalent
mechanism instead of discarding buffer contents. Detect the documented -1
read-error result and return an appropriate HTTP error, while preserving normal
body processing and intervention behavior.

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ℹ️ Review info

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Configuration used: defaults

Review profile: CHILL

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Run ID: 7c25de2e-4b91-42eb-abca-7f4accfeaee9

📥 Commits

Reviewing files that changed from the base of the PR and between 0488c77 and 230e14d.

📒 Files selected for processing (4)

• src/mod_security3.c
• src/mod_security3.h
• src/msc_filters.c
• src/msc_utils.c

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